1. EKT124 Digital Electronics 1 Introduction to Digital Electronics
© 2008 Pearson Education

2. Summary Analog Quantities
Most natural quantities that we see are analog and vary continuously. Analog systems can generally handle higher power than digital systems.
Digital systems can process, store, and transmit data more efficiently but can only assign discrete values to each point.

3. Summary Analog and Digital Systems
Many systems use a mix of analog and digital electronics to take advantage of each technology. A typical CD player accepts digital data from the CD drive and converts it to an analog signal for amplification.

4. Summary Binary Digits and Logic Levels
Digital electronics uses circuits that have two states, which are represented by two different voltage levels called HIGH and LOW. The voltages represent numbers in the binary system.
VH(max)
In binary, a single number is called a bit (for binary digit). A bit can have the value of either a 0 or a 1, depending on if the voltage is HIGH or LOW.
HIGH
VH(min)
Invalid
VL(max)
LOW
VL(min)

5. Summary Digital Waveforms
Digital waveforms change between the LOW and HIGH levels. A positive going pulse is one that goes from a normally LOW logic level to a HIGH level and then back again. Digital waveforms are made up of a series of pulses.

6. Summary Pulse Definitions
Actual pulses are not ideal but are described by the rise time, fall time, amplitude, and other characteristics.

7. Summary Example Solution Periodic Pulse Waveforms
Periodic pulse waveforms are composed of pulses that repeats in a fixed interval called the period. The frequency is the rate it repeats and is measured in hertz.
The clock is a basic timing signal that is an example of a periodic wave.
Example
What is the period of a repetitive wave if f = 3.2 GHz?
Solution
313 ps

8. Summary Pulse Definitions
In addition to frequency and period, repetitive pulse waveforms are described by the amplitude (A), pulse width (tW) and duty cycle. Duty cycle is the ratio of tW to T.
Pulse width (tW)
Amplitude (A)
Period, T

9. Summary Timing Diagrams
A timing diagram is used to show the relationship between two or more digital waveforms,
A diagram like this can be observed directly on a logic analyzer.

10. Summary Serial and Parallel Data
Data can be transmitted by either serial transfer or parallel transfer.

11. Summary AND OR NOT Basic Logic Functions
True only if all input conditions are true.
AND OR
True only if one or more input conditions are true.
NOT
Indicates the opposite condition.

12. Summary Basic System Functions
And, or, and not elements can be combined to form various logic functions. A few examples are:
The comparison function
Basic arithmetic functions

13. Summary Basic System Functions The encoding function
The decoding function

14. Summary
Basic System Functions
The data selection function

15. Summary Basic System Functions The counting function
Counter
Parallel output lines
Binary code for 1
Binary code for 2
Binary code for 3
Binary code for 4
Binary code for 5 1 2 3 4 5
Input pulses
Sequence of binary codes that represent the number of input pulses counted.
…and other functions such as code conversion and storage.

16. Summary Basic System Functions
One type of storage function is the shift register, that moves and stores data each time it is clocked.

17. Summary Integrated Circuits
Cutaway view of DIP (Dual-In-line Pins) chip:
The TTL series, available as DIPs are popular for laboratory experiments with logic.

18. Summary Integrated Circuits
An example of laboratory prototyping is shown. The circuit is wired using DIP chips and tested.
DIP chips
In this case, testing can be done by a computer connected to the system.

19. Summary Integrated Circuits DIP chips and surface mount chips Pin 1
Dual in-line package Small outline IC (SOIC)

20. Summary Integrated Circuits Other surface mount packages:
SOIC PLCC LCCC

21. Summary Test and Measurement Instruments
The front panel controls for a general-purpose oscilloscope can be divided into four major groups.

22. Summary For measuring digital signals, use DC coupling
Test and Measurement Instruments
Normally, trigger on the slower of two waveforms when comparing signals.

23. Summary Test and Measurement Instruments
The logic analyzer can display multiple channels of digital information or show data in tabular form.

24. Summary Test and Measurement Instruments
0.01 V
The DMM can make three basic electrical measurements.
Voltage
Resistance
Current
In digital work, DMMs are useful for checking power supply voltages, verifying resistors, testing continuity, and occasionally making other measurements.

25. Summary Programmable Logic
Programmable logic devices (PLDs) are an alternative to fixed function devices. The logic can be programmed for a specific purpose. In general, they cost less and use less board space that fixed function devices.
A PAL device is a form of PLD that uses a combination of a programmable AND array and a fixed OR array: